Crate mexprp

MEXPRP

A math expression parsing and evaluating library

Usage

There are three different ways to parse and evaluate an equation.

With eval()

This function parses and evaluates a string all at once with the default context. There's also an eval_ctx() function which takes a reference to a Context as well that will be used instead of the default Context.

mexprp::eval("10 / (2 + 3)"); // Ok(2.0)

With Expression

Expression::parse() parses a string into a tree representation (a Term). It can also be parsed with a context with parse_ctx, and it will store that context within it for future evaluations. It can also be evaluated with a reference to any other context with eval_ctx. It's important to ensure that the custom context contains any definitions the Expression depends on.

let expr = Expression::parse("3 ^ 4 / 9").unwrap();
let res = expr.eval(); // Ok(9.0)

With Term

A Term is an Expression, but without any extra overhead.

let term = Term::parse("10 ^ -3").unwrap();
let res = term.eval(); // Ok(0.001)

Using Contexts

You can evaluate expressions with custom variable and function definition's by defining a context. When defining custom functions, it's important to remember to parse the expression with the custom context, or else the parser will recognize your functions as variables instead. Expressions will store the context you parse them with, but you have to evaluate Terms with a reference to a context using Term::eval_ctx. For more info see the context module.

Re-exports

pub use func::Func;

pub use expr::Calculation;

pub use expr::Expression;

pub use expr::Term;

pub use context::Context;

pub use errors::EvalError;

pub use errors::MathError;

pub use errors::ParseError;

Modules

context	Context struct
errors	All the errors
expr	Contains expressions and terms
func	Contains Function trait
op	Contains definitions for Operations
opers	Contains implementations for operations
parse	Contains methods for parsing equations into token representations

Functions

eval	Parse and evaluate a string
eval_ctx	Parse and evaluate a string with the given context